As of patch 0.4.4, players who go inactive are no longer deleted. Rather, all new inactive accounts will be placed into a "ghost" mode, where they will seemingly disappear from the servers. This applies to Ambrosia accounts as well as non Ambrosia accounts.
Any account that was and still is inactive before the patch went live on August 18, 2011, will not be affected by ghosting rules.

The inactivity phases are now:

Phase 0(Hour 0 to Hour 24, sorting the fun registrations out, no long time inactivity): If you do not build anything in the 24 hours after registration, you get deleted.

Phase 1(1 week to 2 weeks after registration ): You become inactive after 2 days with no login, you get ghosted 2 days later.

Phase 2(Week 2 until 1 Month): You become inactive after 7 days with no login, you get ghosted 4 days later.

Phase 3(1 Month until 3 Months): You become inactive after 7 days with no login, you get ghosted 14 days later

Phase 4(3 Month until end of times): You become inactive after 7 days with no login, you get ghosted 30 days later.

Old inactives will remain for the present and are not affected by this change.

Banned users with no ambrosia will be deleted rather than ghosted (no matter if they bought some in the past).